The present application relates to a semiconductor structure and a method of forming the same. More particularly, the present application relates to a method of forming carbon-doped germanium (i.e., Ge:C) stressor regions in an nFET device region of a germanium substrate. The present application also provides a semiconductor structure that is prepared by such a method.
For more than three decades, the continued miniaturization of metal oxide semiconductor field effect transistors (MOSFETs) has driven the worldwide semiconductor industry. Various showstoppers to continued scaling have been predicated for decades, but a history of innovation has sustained Moore's Law in spite of many challenges. However, there are growing signs today that metal oxide semiconductor transistors are beginning to reach their traditional scaling limits. Since it has become increasingly difficult to improve MOSFETs and therefore complementary metal oxide semiconductor (CMOS) performance through continued scaling, further methods for improving performance in addition to scaling have become critical.
The performance of semiconductor device substrates can be modified by exerting mechanical stresses. For example, hole mobility can be enhanced when the channel region is under compressive stress, while the electron mobility can be enhanced when the channel is under tensile stress. Thus, compressive and/or tensile stresses can be provided in the channel regions of a p-channel field effect transistor (pFET) and/or an n-channel field effect transistor (nFET) to enhance the performance of such devices.
For nFETs containing silicon channels, embedded carbon-doped silicon (i.e., Si:C) has been used since the 32 node as a stressor material to enhanced nFET device performance. For future technology nodes, like 7 nm and beyond, unalloyed germanium, i.e., pure germanium, is being considered as the channel material. As such, a stressor material is needed for forming nFET devices having germanium channels. Also, a stressor material is needed that can apply more strain at small volumes as compared with that which can be obtained using Si:C as a stressor material.